Hydraulic braking systems are prevalent among many current vehicles including passenger vehicles. Such braking systems have a master cylinder that holds a brake fluid, and auxiliary cylinders connected the master cylinder to each wheel's dedicated cylinder via a brake line. When the brake pedal of an automobile is actuated, a piston in the master cylinder translates to displace hydraulic brake fluid in the primary cylinder, which in turn forces brake fluid through the brake lines to the auxiliary cylinders at each wheel. The brake fluid in the brake lines is pressurized and imparts a hydraulic force actuating the auxiliary cylinders, which in turn forces a brake pad against the brake drum or rotor of the automobile's wheel. The frictional force of the brake pad against the drum or rotor resists rotation of the wheels themselves, thereby decelerating or stopping the vehicle. Circulating brake fluid can additionally lubricate pistons, cylinders, seals and valves within the brake system.
In order to operate in a variety of conditions, brake fluid is preferably characterized by a high boiling temperature and a low freezing temperature. Moisture in the brake line can form ice at low temperatures that can lead to a loss of fluid flow. Unwanted water absorbed into the brake fluid leads to a reduced boiling temperature and the formation of ice, which causes poorer brake performance. Contamination is also an issue for effective operation of the braking system, where breakdown of the fluid can lead to premature wear of piston seals, hoses and other parts. Additionally, oxidation of the brake fluid upon exposure to air can result in a reduced boiling temperature. Additionally the additive packages used in brake fluids to reduce oxidation, foaming and corrosion are denigrated by the presence of moisture.
Because the introduction of unwanted moisture and contaminants in the braking system is unavoidable, automobile manufactures recommend that automotive brake fluid should be replaced and the brake system flushed of contaminants when the moisture level in the brake fluid exceeds a predetermined threshold, when contamination is present, or when the hydraulic fluid's inhibitor package has deteriorated.
Brake fluids for passenger vehicles are usually clear, volatile, water-soluble liquids comprised of a mixture of several alcohols such as glycols, although Silicone-based brake fluids are also known. Through use, brake fluid can become discolored due to contamination from dirt and disintegrating rubber seals. Furthermore, as the brake fluid absorbs moisture from the air, its boiling point is lowered and corrosion may initiate inside the brake system. A reduced boiling point can result in the brake fluid boiling under extreme conditions such as a long downhill stretch of intermittent braking. Bubbles in the brake fluid due to boiling reduce the brake effectiveness because gas is very compressible as compared with fluid, and thus the force applied by the pressurized brake fluid in the brake lines is lessened as the amount of gas in the system increases.
Particulate matter such as airborne dust and rubber seal fragments can also collect within the fluid filled brake lines preventing proper sealing of valves within the braking system. To remove water and contaminants the brake fluid is periodically removed and replaced with new brake fluid, thereby restoring the brake fluid's preferred temperature range, corrosion resistance and braking efficiency. However, care must be taken to prevent exposure to air by the fresh brake fluid. Brake fluid exposed to ambient air can absorb moisture resulting in an immediate loss of the brake fluid's effectiveness. Typically, the entire hydraulic fluid is drained from the brake system and replaced with new fluid, the whole operation being carried out in an open-air environment whereby the fluid is exposed to the atmosphere as the brake system is being drained and new fluid is added. Unfortunately this known method can release pollutants into the air and exposes the operator to potentially harmful fluids and vapors.
Prior art brake fluid exchange machines typically required two workers to complete the job. A first worker would start the engine and pump the brake pedal while the second worker monitored the fluid exchange machine as it vacuumed the old fluid and then pumped in the new fluid. The job typically took up to thirty minutes and was not cost effective in that two workers must be present for essentially the entire job. Moreover, the brake fluid exchange process did not account for the varying lengths of brake line, adding inefficiencies and undue delays in the fluid exchange process. Thus, there is a need in the industry for an automated brake fluid replacement system that connects to the braking system of a vehicle and allows a single worker to complete the task in less time than previous systems.